The Super Rokkor 50/2.8 is a really fine lens, not unlike the 45/2.8 it replaced. It makes real nice images, somewhat Tessar-like wide open, with a sharp center graduating smoothly to less sharp edges. Out-of-focus imagery is very pleasing and contrast is medium. I like to use the 45mm more (one of my favorite lenses), probably for it's size, ergonomics, slightly wider view, and that it seems to be built a bit better than the 50mm. The 50mm does have a 40.5mm filter ring, which is convenient.
It is not a classical Heliar design, but not a Tessar either. Both the Super Rokkor 50/2.8 and 45/2.8 have a 5e/2g design, with a cemented triplet up front and a cemented doublet in back. The red "C" indicates a coated lens. Regarding the coverage and vignetting: I have never noticed a problem. Besides, i think the Super Rokkor 50mm came with the Minolta 35 II, which switched to the standard frame size. Anyway, the 50/2.8 and 45/2.8 work fine on standard-sized film gates.
I have never used the Industar-61LD, so I cannot comment on that. The Super Rokkor 50/2.8 is better, I think, than the Canon 50/2.8, but not as sharp as the Canon 50/1.8. I have always found the Canon 50/1.8 to be very sharp, with lower contract, but not very memorable either -- kind of plain, I guess. The Super Rokkor has a nicer look to me, a bit rounder with more character.
(All of this "imagery", "character", and "signiture" stuff is hard to define and highly subjective - take some pictures and then take my word for it 😉 )
For a real treat, hunt down the Super Rokkor 50/2 and 50/1.8 lenses. The 50/2 is a real keeper, and the 50/1.8 is a killer -- as good or better than any f2/f1.8 lens from that era, Nikon, Canon, Zeiss, and Leitz included. Too bad they made so few; it is easier to find a Minolta Super-A to use those lenses (i.e., same lenses, different mount). But, i digress.
Cheers,
David